For a stronger repair, rather than drilling an oversize hole, you should drill a normal size hole, and then use a router bit to carve out the core between the upper & lower skins.

Then duct-tape the hole from the bottom, paint the exposed core in the hole with epoxy, and fill with thickened epoxy (with colloidal silica - some of the other thickeners will wick water down thru the epoxy). You coat the exposed core with unthickened first because the wood will suck up epoxy otherwise, and end up sucking epoxy, leaving an epoxy-poor plug.

This results in a plug of thickened epoxy sandwiched between two fiberglass skins, so it can't pop up and out if there's a vertical load on whatever hardware you're attaching.